This invention relates to protection of high power switching transistors in a D.C.-A.C. inverter of the type in which the on-off control signal to the transistors is modulated at a relatively high frequency combined with the 60 Hertz frequency.
In this type of inverter, using a "quad" of four transistors in a bridge configuration, failure of certain components in the control circuits could cause millisecond instead of microsecond pulses to be applied to the power transistors, causing current to build up to levels far in excess of their rating.